Damascene processing is a method for forming metal lines on integrated circuits. It involves formation of inlaid metal lines in trenches and vias formed in a dielectric layer (inter layer dielectric or ILD). Damascene processing is particularly well-suited to metals such as copper that cannot be readily patterned by plasma etching.
In a typical Damascene process flow, copper or other metal is deposited onto a patterned dielectric to fill the vias and trenches formed in the dielectric layer. A thin layer of a dielectric diffusion barrier material, such as silicon carbide or silicon nitride, is deposited between adjacent metallization layers to prevent diffusion of metal into bulk layers of dielectric. In some cases, the silicon carbide or silicon nitride dielectric diffusion barrier layer also serves as an etch stop layer during patterning of the inter layer dielectric layer.
In a typical integrated circuit (IC), several metallization layers are deposited on top of each other forming a stack, where metal-filled vias and trenches serve as IC conducting paths. The conducting paths of one metallization layer are connected to the conducting paths of an underlying or overlying layer by a series of Damascene interconnects.
Fabrication of these interconnects presents several challenges, which become more and more significant as the dimensions of IC device features continue to shrink. There is a strong need for interconnect fabrication methods that can provide interconnects with improved lifetime and reliability.